Scratch test of thermoplastic denture base resins for non-metal clasp dentures.

PURPOSE: Several thermoplastic denture base resins have been introduced for the fabrication of non-metal clasp dentures. Although the surface of these materials is easily damaged, the surface roughness and characteristics of scratches created have not been evaluated. The purpose of this study was to evaluate the surface roughness of thermoplastic resins using a scratch test for the development of future materials. METHODS: Four thermoplastic (polyamide: Valplast((R)); VLP and Lucitone FRS((R)); FRS, polyethylene terephthalate: EstheShot((R)); ES, and polyester: EstheShot Bright((R)); ESB) and two conventional acrylic (Heat-polymerizing: Urban((R)); HC, and Pour type auto-polymerizing: Pro-Cast DSP((R)); PR) denture base resins were examined. Eight specimens, approximately 10mmx10mmx30mm in size, of each material were fabricated. Scratch test was performed by a scratch tester with a diamond indenter of 10-mum radius and cone angle 90 degrees , applying a constant load of 500mN, and 2-mm-long scratches were made. The scratch marks were studied under 3D laser measuring microscope and cross-section profiles at approximately 0.5mm, 1.0mm, and 1.5mm from the starting point were extracted and measured with analysis software. Data from 24 cross-section profiles in each denture base material were analyzed. RESULTS: The maximum depths of ES, ESB and FRS were greater than VLP, PR and HC, and the scratch widths of ES, ESB, FRS and VPL were greater than PR and HC. CONCLUSIONS: The results showed that the surface of thermoplastic denture base resins was easily damaged compared to polymethyl methacrylate.